Engines including in their structure elements normally found only in hot-air engines and other elements normally found only in internal-combustion engines and having steps in their cycle of operation peculiar to both such types of engines. This subclass includes engines including elements selected from both the above-mentioned types and convertible either at will or automatically, as by a suitable governing device, so as to operate either as hot-air or as internal-combustion engines, and engines operating upon a predetermined cycle, including working strokes, upon which the piston is impelled
alternately by gases heated within the working cylinder by combustion, as in internal-combustion engines, and by gases heated within the working cylinder by contact with the inner surface of said working cylinder and the clearance-space.
